Vacuum-coating machine with motor-driven rotary cathode

ABSTRACT

In a vacuum-coating machine ( 1 ), the drive unit ( 6 ) is mounted compliantly to the chamber housing ( 3 ) by means of an elastic intermediate plate ( 14 ), such that said drive unit can follow a wobbling motion imposed by the rotary cathode ( 10 ), with the support bearing ( 19 ) of the free end of the rotary cathode ( 18 ) capable of being of a rigid design.

This application is a continuation of U.S. patent application Ser. No.11/501,286, filed Aug. 9, 2006, entitled VACUUM-COATING MACHINE WITHMOTOR-DRIVEN ROTARY CATHODE, by Applicant Andreas Sauer, which isincorporated by reference herein in its entirety.

The present invention concerns a vacuum-coating machine withmotor-driven rotary cathode and a device for compensating a wobblingmotion of the rotary cathode, in accordance with the generic part ofclaim 1.

In vacuum-coating technology, increasing use is being made of rotatingcoating cathodes (rotary cathodes), one end of which is flange-mountedto a drive unit, usually at the chamber housing of the process chamberaccommodating the rotary cathodes. The rotary cathodes may be arrangedhorizontally or vertically in the vacuum-coating machine. The first ofthese (horizontal vacuum-coating machines) are used, for example, forglass coatings, and the second (vertical vacuum-coating machines), forexample, for display coatings. The rotary cathodes are generallydesigned as a tubular target rotating about the longitudinal axis with apermanent magnet system inside the tube. The magnetic field emanatingfrom there permeates the target material, as a result of which thefamiliar magnetron effect occurs. The rotation leads to highly uniformwear of the tubular target, and so prolongs service lives and reducescosts. Furthermore, a cooling system may be accommodated inside thetube. Two design principles are generally distinguished for horizontallyarranged rotary cathodes. In the first principle, the complete driveunit, including the power and coolant feed (media feed), is arranged atthe lid of the vacuum-coating chamber, by means of so-called end blocksor bearing blocks at one end of a rotary cathode, as shown in patentU.S. Pat. No. 4,445,997. An improved embodiment in which the end blocksor bearing blocks are arranged outside the process chamber to facilitatemedia feed, is shown in DE 100 04 787 A1. Basically, this designprinciple proves to be awkward, however, when the rotary cathodes ortubular targets are changed, since the entire unit, including thechamber lid, has to be removed from the vacuum-coating machine. In thesecond design principle, the drive unit, including the media feed, ismounted to the chamber outer wall, a fact which generally simplifieshandling. When the rotary cathode or the tubular target is changed, it,including the magnet and cooling system located inside the tube, isremoved from the flange of the drive unit and, with the chamber lidopen, lifted out of the vacuum-coating chamber. Machines of this typeare shown, for example in U.S. Pat. No. 5,200,049.

Up to a certain tube length, the rotary cathode may be designed as afreely projecting, i.e. cantilever, design. Especially in the case oflong rotary cathodes, however, the increasing weight moment loadnecessitates additional support by means of a support bearing, usuallyat the free end of the rotary cathode.

Two design principles may be distinguished for tubular targets. Thetubular targets of the first principle are mechanically stable,thick-walled tubes. The tubular targets of the second principle are verythin-walled tubes in which the actual target material (such as Si, Zn,SiAl), is applied to a mechanically stable support tube, for example bycasting, plasma spraying or thermal joining (bonding). A shared featureof the tubes of both design principles is that, due to the temperaturewarping introduced during manufacture, they have to a certain degreespatially curved tubular axes, which cannot be re-worked, for example,straightened, because the materials are hard, brittle and frangible.These curved tubular target axes (longitudinal axes of the tubulartargets) cause a wobbling motion of double amplitude when the rotarycathode is firmly clamped on one side at the opposite free end of therotary cathode. Given a maximum tube length of 4 m, deviations intubular axis of 10 mm are no rarity, a fact which leads to a wobblingmotion of +/− 10 mm. To ensure adequate support in spite of thiswobbling motion at the free end of the rotary cathode, mostlyspring-mounted supports are used there that follow the wobbling motionand are able to damp them. Such a support is described, for example, inU.S. Pat. No. 5,620,577. The supporting force may be adjusted bypre-tensioning at least one spring.

The known solutions to the underlying problem, i.e. support for awobbling rotary cathode, have various disadvantages, however. Whentubular targets of different weights are used, the spring pre-loading ofthe support bearing must be adjusted to the respective weight of thetubular target. Further, when the tubular target describes a fullrotation, the supporting force fluctuates by an amount calculated fromthe spring rate of the spring system and the wobbling deflection. Sincethe mass of the tubular target decreases during operation as a result ofsputter erosion (down to as much as 20% of the original weight), thesupporting force ideally must be readjusted during operation. Theconstantly changing conditions ultimately also lead to extreme bearingloads in the support bearing and thus to premature wear. Attempts aretherefore made to dimension the support bearing to the maximum loadingcase, a fact which in turn leads to large bearings and thus associatedhigh costs.

Patent EP 1 365 436 A2 describes a rotary cathode drive which alreadyimplements design measures for drive-side compensation of wobblingmotions. This is effected by suspending the gear unit movably in anenclosing housing and via gearing play in the drive assembly. From adesign point of view, limits are thus imposed on the degrees of freedomfor compensating wobbling motions. Furthermore, retrofitting existingmachines with such rotary-cathode drives proves to be disadvantageous asthis can only be done at high design and financial outlay. The latterconsideration basically concerns the construction of new machines aswell, which becomes correspondingly more expensive.

The object of the invention is to provide a rotary-cathode bearingwhich, on one hand, can follow and damp the wobbling motion of therotary cathode, but, on the other, does not require readjustment, andfurther facilitates simple changing of the rotary cathode or tubulartarget. At the same time, the solution to the problem should also beapplicable to existing machines and comparatively inexpensive.

This object is achieved in accordance with the invention having thefeatures of the characterizing part of claim 1. The features of thesubsequent sub-claims indicate advantageous further developments.

The invention is based on the consideration of intercepting the wobblingmotion imposed by the rotary cathode (more accurately by the tubulartarget) not on the side of the support bearing, but rather essentiallyon the drive side. To this end, the entire drive unit to which therotary cathode is compliantly flange-mounted, that is to say movably ina defined measure, is mounted to the chamber housing, especially to alateral chamber outer wall. This is effected by arranging an elasticintermediate plate at the connecting point (mounting flange) betweendrive unit and chamber housing, said intermediate plate beingexpediently formed from an elastomer and preferably by a thick rubberslab. With this elastic intermediate plate, the drive unit is nowcapable of executing the wobbling motion imposed by the rotary cathode,with the support bearing of the free rotary cathode end now capable ofhaving a rigid design. Since, on account of the rigid design, weightmoments no longer act upon the support bearing, but rather just theweight force equivalent to half the rotary-cathode mass, this supportbearing can now have smaller overall dimensions overall, a fact whichfrees up construction space and saves on costs. Further, readjustment ofa spring pre-load becomes superfluous.

Because the material of the intermediate plate is elastic, a vacuum sealis automatically obtained, with the result that further sealing measuresfor sealing the process chamber at this point are unnecessary orhitherto measures of sealing the drive side can be dispensed with.

The invention is therefore also of particular interest since existingvacuum-coating machines can be retrofitted cost effectively, with theexisting drive units, including all their feed mechanisms (media feed),capable of being further used. For the construction of new machines,too, the design and financial outlay for implementing the invention arecomparatively low.

By way of an initially unexpected advantage, it has furthermore emergedthat the inclination angle of the rotary cathode relative to the chamberwall, which typically is in the region of 90°, can be selectivelyaltered within a certain range of degrees on account of the elasticbehavior of the intermediate plate.

A further advantage is that the intermediate plate markedly reducesvibrational transmission from the drive unit to the vacuum-coatingchamber, a fact which increases production quality and contributes tonoise reduction.

If the intermediate plate is formed from an electrically nonconductingmaterial, it may simultaneously serve as an isolator between the chamberand the cathode potential. Other isolation measures, such as theinstallation of an isolation block, may thus be dispensed with.

Depending on the design of the intermediate plate, especially themounting technology, longitudinal expansion of the rotary cathode, forexample as a result of heating and cooling, can be compensated as well,a fact which hitherto had necessitated the use of additional designmeasures if high loads in the support bearing or in the drive unit wereto be avoided. (The background to this paragraph is citation EP 1 365436 A2)

The enclosed drawings are intended to describe a concrete embodiment ofthe invention in more detail. In it,

FIG. 1 a cross-sectional representation of a horizontal vacuum-coatingmachine with a rotary cathode of the prior art

FIG. 2 is a cross-sectional representation of a horizontalvacuum-coating machine with the drive-unit suspension in accordance withthe invention

FIG. 3 a detailed view of the connecting point between drive unit andchamber wall in cross-section

FIG. 4 a detailed view of the connecting point between drive unit andchamber wall in cross-section with an alternative connecting technology

FIG. 1 shows a horizontal vacuum-coating machine 1 in accordance withthe prior art. A process chamber 2 is limited by lateral chamber walls4, a chamber floor 15 and a chamber lid 5, which facilitates access tothe process chamber for maintenance and repair work. Inside the processchamber 2 is arranged at least one rotary cathode 10, in this embodimentwith a tubular target. The rotary cathode could equally have a soliddesign, however. Not shown are the usual prior-art fixtures installedinside the tube cathode, for example a magnet and/or cooling system andthe like. For reasons of clarity, means of support and transport withinthe process chamber 2 for the work pieces to be processed are not showneither. These means are known to an expert skilled in the art, so that adescription is superfluous. One end of the rotary cathode 10 isconnected, preferably rigidly flange-mounted, through a wall opening 16in the lateral chamber wall 4, to a drive unit 6. The drive unit 6 ismounted to the chamber outer wall 41, for example with fixing screws 9,and comprises a drive motor 7 and a gear/coupling block 8, with thelatter also comprising the mounting on this side for the rotary cathode.Both the rotary movement and the media required for the process, such ascoolants, are thus introduced or fed from the side into the drive-sideof the process chamber. For changing the rotary cathodes 10, the rotarycathode is removed from the flange of the drive unit 6 and, along withall its fixtures, lifted upwards through the opened chamber lid 5 andout of the process chamber 2.

To keep the weight moment load that emanates from the rotary cathode onthe drive unit 6 and its mounting means low, the free end 18 of therotary cathode, i.e. the end opposite the flange, is supported by asupport bearing 19. In the embodiment of FIG. 1, the rotary cathode 10is to this end continued by a shaft journal 17, which is accommodated bya rolling bearing 12, with the rolling bearing 12 mounted to a support11. In the embodiment shown, the support bearing 19 is arranged insidethe process chamber 2, it is however also possible to effect the supportoutside the process chamber 2, for which purpose the rotary cathode 10or a continued shaft journal 17 has to be fed through a correspondingopening in the lateral chamber wall 4, a fact which entails additionaldesign outlay. As a consequence of production tolerances andmanufacturing-related thermal warping of the tubular target, the rotarycathode has, to a certain degree, a spatially curved tubular axis, withseveral radii of curvature and curvature directions all capable of beingpresent in a rotary cathode. As a consequence of the rigid mounting ofthe rotary cathode 10 to the drive unit 6, the free end of the rotarycathode 18 thus executes a multi-dimensional wobbling motion duringrotation. In order to be able to follow this wobbling motion, thesupport bearing 19 has a spring system 13, with the embodiment in FIG. 1not showing damping and pre-loading elements. Pre-loading and/or dampingof the spring system 13 has to be manually readjusted to an extentdepending on the rotary cathode 10 installed and on target materialwear.

If the axis of the rotary cathode 10 is not at the correct anglerelative to the chamber wall 4, for example at a 90° angle, the angle ofinclination of the rotary cathode 10 may be altered relative to thechamber wall 4 by differentially tightening the fixing screws 9, i.e. bydifferentially compressing the intermediate plate 14. This is alsoespecially of interest for the retrofitting of existing machines since,in this way, with the aid of a centering tool, the driven-shaft axis ofthe drive unit 6 can be aligned with the center of the support bearing19 opposite. This also means that it is possible to align the drive unit6 with the rotary-cathode axis.

For reasons of clarity, the embodiment of FIG. 1 does not show means ofisolation, for example in the form of an isolation block, which, asnecessary, isolates the various electrical potentials between rotarycathode 10 and drive unit 6 on one side and the chamber housing on theother.

FIG. 2 shows a horizontal vacuum-coating machine with the invention'scompliant suspension of the drive unit 6 at the chamber housing 3. Thereference labels for the individual components are identical with thoseof FIG. 1. In accordance with the invention, the drive unit 6 does notmake direct contact with the chamber outer wall 41, but ratherindirectly via a compliant intermediate plate 14, which has elasticmaterial properties. The intermediate plate 14 here has, for example,the shape of an annular disk. As a consequence of the compliantsuspension effected by the intermediate plate 14, the drive unit 6flange-mounted to the rotary cathode 10 can now follow the wobblingmotion of the rotary cathode, so that the support for the free end ofthe rotary cathode 18 may be executed as a rigid support. This thusobviates the need for re-adjustment or manual re-setting of a springsystem in the support bearing 19. As a consequence of the lower momentand tensile loading on the roller bearing 12, the latter can now havesmaller dimensions.

FIG. 3 shows a simple and cost-effective technology for mounting thedrive unit 6 to the chamber outer wall 41 using an elastic intermediateplate 14. The drive unit 6 is mounted here to the chamber wall 4 bymeans of fixing screws 9, with the screw shafts extending right throughvia drilled holes in the drive unit 6 and the intermediate plate 14, andthe screw threads engaging with corresponding counter-threads in thechamber wall 4. The drive unit 6 thus does not make direct contact withthe chamber outer wall 41, but rather via an elastically compliantintermediate plate 14, as already described above. On account of thenon-rigid connection, the drive unit 6 possesses a certain degree ofmobility relative to the chamber wall 4. Should electrical isolation ofthe various potentials of chamber housing 3 and drive unit 6 benecessary, so-called isolation sleeves for the screws 9 (not shown) maybe used.

FIG. 4 shows an alternative technology for mounting drive unit 6 to thechamber wall 4. An advantage of this more elaborate mounting technologylies in the extended degrees of movement of drive unit 6 relative to thechamber wall 4. The intermediate plate 14 is mounted here by screws 92to the lateral chamber wall 4 via drilled through-holes. To an extentdepending on the arrangement of the screws 92, it may be necessary toprovide counter-sinking for the screw heads. The drive unit 6 is mountedto the intermediate plate 14 by means of fixing screws 91. For this, itmay be necessary to reinforce the threads inside the intermediate plate14, for example by means of metallic thread inserts. The design ideahere is that the means of mounting do not create a rigid connectionbetween drive unit 6 and chamber wall 4. A further advantage of thismounting technology is that, on account of the underlying principle, thevarious potentials of chamber housing 3 and drive unit 6 areelectrically isolated.

In a further embodiment not shown, mounting bolts pass from the driveunit 6 through the intermediate plate 14 and are secured to the backside of intermediate plate 14, i.e. the side facing the chamber wall 4,for example with nuts, for which purpose the design must provideappropriate space. Other connecting technologies and methods are alsoconceivable, however.

In order that intermediate plate 14 may also produce a vacuum sealbetween chamber wall 4 and drive unit 6, the chamber outer wall 41 mustbe reworked at the corresponding point (surface section) in order that asurface of sealing-surface quality may be obtained, with the necessarysurface quality critically depending on the intermediate plate 14employed. In the embodiment shown in FIG. 4, therefore, a recessed wallarea (cutout, recess) 42 is shown which corresponds to such a reworkedsurface section. It is also conceivable, however, for the surfacesection to be formed not as a recessed wall area, but as a projectingwall area. In the case of a recessed wall area 42, the advantage is thatof simplified assembly.

The intermediate plate 14 is formed from an elastomer, preferably from arubber material, especially from a natural rubber or silicone. The Shorehardness is 50° minimum and 80° maximum. A range of 60° to 70° Shorehardness is preferred. It goes without saying that such materials areelectrically isolating. Materials for the intermediate plate 14 areobtainable on the market as semi-finished goods of the most diverseproperties.

The idea of the invention is not limited to horizontal vacuum-coatingmachines, it is therefore also possible for an expert skilled in the artto implement it in a vertical vacuum-coating machine in which the freeends of the cathodes are also supported. It is equally conceivable forthe features of the various embodiments described to be combined.

List of Terms

-   1 Vacuum-coating machine-   2 Process chamber-   3 Chamber housing-   4 Chamber wall-   5 Chamber lid-   6 Drive unit-   7 Motor-   8 Gear/coupling block including bearing-   9 Fixing screws (drive unit/chamber wall)-   10 Rotary cathode (tubular target)-   11 Support-   12 Rolling bearing-   13 Spring (with pre-loading and damping)-   14 Intermediate plate-   15 Chamber floor-   16 Wall opening-   17 Shaft journal-   18 Free end of rotary cathode-   19 Support bearing-   20 Metallic thread insert-   41 Chamber outer wall-   42 Cutout, recess-   91 Fixing screws (drive unit/intermediate plate)-   92 Fixing screws (intermediate plate/chamber wall)

1. A vacuum-coating machine comprising: at least one process chamberwith a chamber housing; at least one rotary cathode supported relativeto the chamber housing, the rotary cathode driven by a drive unit, whendriven said rotary cathode exhibiting a wobbling motion; wherein therotary cathode is rigidly connected through a wall opening in a lateralchamber outer wall of the chamber housing at a connecting point to thedrive unit; and wherein at the connecting point between the drive unitand the rotary cathode the drive unit is arranged by a compliantsuspension relative to the lateral chamber outer wall, and the compliantsuspension of the drive unit includes an intermediate plate arrangedbetween the lateral chamber wall and the drive unit, and said compliantsuspension allowing said drive unit to follow the wobbling motion of therotary cathode.
 2. The vacuum-coating machine in accordance with claim 1wherein the drive unit is mounted to the chamber outer wall by fastenerswhich extend through drilled holes in the drive unit and theintermediate plate.
 3. The vacuum-coating machine in accordance withclaim 1, wherein the intermediate plate is mounted only to the chamberhousing and the drive unit is mounted only to the intermediate plate. 4.The vacuum-coating machine in accordance with claim 1, wherein thechamber housing includes a wall opening, the drive assembly having adrive assembly fed with a diameter, the rotary cathode having a wobblingdeflection, the wall opening being at least that of the diameter of thedrive assembly fed plus twice the wobbling deflection of the rotarycathode.
 5. The vacuum-coating machine in accordance with claim 1wherein the intermediate plate is formed from an elastomer.
 6. Thevacuum-coating machine in accordance with claim 5, wherein the elastomercomprises a rubber material.
 7. The vacuum-coating machine in accordancewith claim 6, wherein the rubber material comprises a natural rubber orsilicone.
 8. The vacuum-coating machine in accordance with claim 5,wherein the elastomer has a Shore hardness of 50° minimum and 80°maximum Shore hardness.
 9. The vacuum-coating machine in accordance withclaim 8, wherein the Shore hardness is in a range of 60° to 70° Shorehardness.
 10. The vacuum-coating machine in accordance with claim 1,wherein the intermediate plate is formed from an electricallynonconducting material.
 11. The vacuum-coating machine in accordancewith claim 1, wherein the rotary cathode is supported by a supportbearing at a free end of the rotary cathode.
 12. The vacuum-coatingmachine in accordance with claim 11, wherein the support bearingcomprises a rigid bearing.
 13. The vacuum-coating machine in accordancewith claim 1, wherein the chamber outer wall has a surface section forcontact with the intermediate plate.
 14. The vacuum-coating machine inaccordance with claim 13, wherein the surface section includes a cutoutor recess.
 15. A vacuum-coating machine comprising: a chamber housing;at least one rotary cathode, the rotary cathode supported relative tothe housing, the housing having a chamber outer wall; and a drive unitdriving the rotary cathode through the chamber outer wall, when driventhe rotary cathode exhibiting a wobbling motion, the drive unit mountedto the chamber outer wall with a non-rigid connection, said non-rigidconnection providing at least one degree of freedom of movement for thedrive unit relative to the chamber wall, and the drive unit rigidlycoupled to the rotary cathode in a manner so that the drive unit followsthe wobbling motion of the rotary cathode, and the non-rigid connectioncomprising an intermediate member arranged between the chamber outerwall and the drive unit allowing the drive unit to follow the wobblingmotion of the rotary cathode.
 16. The vacuum-coating machine accordingto claim 15, wherein the intermediate member is formed from an elastomermaterial.
 17. The vacuum-coating machine according to claim 16, whereinthe drive unit is mounted to the intermediate member and theintermediate member is mounted to the chamber wall wherein the driveunit has at least two degrees of freedom of movement relative to thechamber wall.
 18. The vacuum-coating machine according to claim 16,further comprising a support, wherein the drive unit is rigidly coupledto one end of the rotary cathode, the support providing a rigid supportfor the other end of the rotary cathode.
 19. The vacuum-coating machineaccording to claim 18, wherein the chamber outer wall has an opening,the rotary cathode having a range of wobbling motion, the drive unitdriving the rotary cathode through the opening, wherein the opening issized greater than the range of wobbling motion of the rotary cathode.20. The vacuum-coating machine according to claim 16, wherein theelastomer comprises a natural rubber or silicone.